Custom schema storage
By default, Pulsar stores data type schemas in Apache BookKeeper (which is deployed alongside Pulsar). You can, however, use another storage system if you wish. This doc walks you through creating your own schema storage implementation.
In order to use a non-default (i.e. non-BookKeeper) storage system for Pulsar schemas, you need to implement two Java interfaces: SchemaStorage
and SchemaStorageFactory
.
SchemaStorage interface​
The SchemaStorage
interface has the following methods:
public interface SchemaStorage {
// How schemas are updated
CompletableFuture<SchemaVersion> put(String key, byte[] value, byte[] hash);
// How schemas are fetched from storage
CompletableFuture<StoredSchema> get(String key, SchemaVersion version);
// How schemas are deleted
CompletableFuture<SchemaVersion> delete(String key);
// Utility method for converting a schema version byte array to a SchemaVersion object
SchemaVersion versionFromBytes(byte[] version);
// Startup behavior for the schema storage client
void start() throws Exception;
// Shutdown behavior for the schema storage client
void close() throws Exception;
}
For a full-fledged example schema storage implementation, see the
BookKeeperSchemaStorage
class.
SchemaStorageFactory interface​
public interface SchemaStorageFactory {
@NotNull
SchemaStorage create(PulsarService pulsar) throws Exception;
}
For a full-fledged example schema storage factory implementation, see the
BookKeeperSchemaStorageFactory
class.
Deployment​
In order to use your custom schema storage implementation, you'll need to:
- Package the implementation in a JAR file.
- Add that jar to the
lib
folder in your Pulsar binary or source distribution. - Change the
schemaRegistryStorageClassName
configuration inbroker.conf
to your custom factory class (i.e. theSchemaStorageFactory
implementation, not theSchemaStorage
implementation). - Start up Pulsar.